ON 20100610@5:57:39 PM at page: On a web page you were interested in at: http://www.sxlist.com/io/stepper/linistep/faq.htm#40330.2925810185 James Newton[JMN-EFP-786] Published and replied to post 40330.2925810185 by e2w |Insert 'Change the sense resistors to provide more current to the motors? Assuming they can take it.' at: '' e2w@earthlink.net asks:
I have four of the old version 1 controllers and was going to use on Taig mill. Thats 20tpi leadscrew. It appears the best speed IPM I can get with Version one is max of 240 RPMs which comes out to 12IPM table speed. Is there anything I can do to improve on that?
|Delete 'P-' before: '' but after: 'mail@mmccoo.com asks:


Hi,

Thank you for the linistepper website. great stuff. I've been studying it for the last week or so.

I have a question on the current sensing aspect of the circuit.

When the input to the bc337 device is low/gnd, that device is effectively an open circuit. If the sinking output of the pic (connected to the reverse diode and 220ohm) is high that leaves us with a direct path from 5v through 470 and 120 (r14, r15) to the tip122. There be a small voltage drop to tip122 base due to Ibe, but it'll be pretty close to 5v.

If we assuming a Vbe of 2v, TIP122 will try to maintain ~3v on the current sensing resistor. A 3v drop across 1 ohm is 3 amps.


This doesn't match the spec of 1 amps for the driver. Where did I go wrong?


As a secondary question, in the current sensing ascii art explanation, you have a resistor parallel to the 2.2uf cap. I don't see a resistor in the schematics. I'm guessing that you're referring to the 120ohm when the bc337 device is on. when it's on, the 120ohm acts as a voltage divider with the pic outputs/diodes/resistors.

Did I get that right?


Either way, I love the simplicity of the system. I have a chopper driver for my machine now and I really don't like it. I get a ton of noise, the motors aren't being driven to their potential (at least I don't think they are). I think a solution like this is what I've been looking for.

Miles
|Delete 'P-' before: '' but after: 'jeffery.seiffert@gmail.com asks: " Hi, Who makes the blue terminal strips, or where do you purchase them from?

Thanks,

Jeff
"
  • ' ON 20100629@4:52:32 PM at page: On a web page you were interested in at: http://www.piclist.com/io/stepper/linistep/faq.htm#40358.5407291667 James Newton[JMN-EFP-786] Published and replied to post 40358.5407291667 by nmakarov3 |Insert 'As long as labview can generate a "step" pulse when it wants the motor to move to the next position, and hold a "direction" line high or low depending on the desired direction of rotation, then it can work. The linistepper is a standard step and direction driver, just like all the rest.' at: '' nmakarov3@mail.gatech.edu asks: " Hi,
    we are looking for a cheap stepper motor driver controllable over LabView. Is this possible with this one?
    Thanks,
    Nikolay." |Delete 'P-' before: '' but after: 'kenneth.cummins@gmail.com asks:
    I'm looking at possibly getting a LiniStepper (or three) to drive Vexta PK266-02A motors (3.6V @ 2A per phase, unipolar), an dI'm trying to figure out the modifications I would need to make to the resistor values. I know I'll need to add a 1 ohm resistor in parallel with the existing sense resistor, but I can't for the life of me figure out the changes to R14-17 and R18-29 that are implied in this tuning page. Am I still "close enough" to spec to use the components given? If not, how do I calculate what the new values should be? It looks like R18-19 and R24-25 pair with R14-15 and R16-17 as a voltage divider, but I can't, for the life of me, figure out what the remaining resistors do. I assume it's another voltage divider, but the diodes have me stumped... If you could help me understand what they do, and how I would need to modify the values, I'd appreciate it!
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